The present invention relates to a boat propeller. More particularly this invention concerns a variable-pitch boat propeller whose vanes can be set manually.
A standard variable-pitch boat propeller as described in my U.S. Pat. No. 4,897,056 has a hub shaft that is rotated by the boat""s engine about a hub axis and that carries a plurality of vanes extending radially of the hub axis and pivotal about respective vane axes extending generally radially of the hub axis. An adjustment element on the hub is axially displaceable and is coupled via respective eccentric mechanisms to the vanes so that, as the adjustment element is shifted axially, the vanes all pivot synchronously about their respective axes. In this manner the pitch of the vanes can be changed for different drive characteristics. The adjustment element is typically mounted via a screwthread on the hub so that as it it rotated it moves axially and changes the vane setting.
In the standard system a knob is mounted on or actually formed as part of the adjustment element. In order to ensure that the vane settings do not drift, the knob is set to lock on the hub except when it is pulled back against a spring force. The boat operator can therefore pull the knob back and rotate it to change the vane setting.
This system provides a wide range of variation of settings for the propeller vanes. In practice, however, the propeller is normally used in only two different positions. For instance a boater who periodically pulls water skiers will have a normal-travel setting and a water-ski setting. Finding these settings, even if there are indicia on the drive, is difficult, normally requiring that the drive be lifted. Under the best of circumstances, finding a particular setting is difficult.
It is therefore an object of the present invention to provide an improved variable-pitch boat propeller.
Another object is the provision of such an improved variable-pitch boat propeller which overcomes the above-given disadvantages, that is which can easily be switched between different settings.
A variable-pitch boat propeller has according to the invention a hub rotatable about a hub axis, a plurality of vanes rotatable on the hub and extending generally radially of the hub axis, and an adjustment element rotatable on the hub about the hub axis and connected to the vanes for pivoting the vanes on the hub. An adjustment knob is pivotal on the hub about the hub axis and interengaging formations on the knob and hub limit angular displacement of the knob on the hub between a pair of end positions so that a limited range of adjustment of the vanes is possible with the knob.
Thus with this system the sleeve is positioned such that, once the knob is in place, it can be easily shifted between a pair of predetermined positions. Thus the sleeve is normally set in the shop for an ideal normal-travel direction and the knob is fitted in place so that the sleeve can be rotated out of this preset position through, say, 100xc2x0 to another position ideal for water skiing, for example. The user of the boat can merely shift the knob between end positions to get the only two vane positions that are normally needed. Of course if the knob is removed and reset in another position, the end positions can be changed.
The propeller further has according to the invention at least one fastener releasably fixing the knob against axial movement on the adjustment element. This fastener is a screw extending radially of the hub axis in the knob. The adjustment element is formed with a groove open radially outward relative to the hub axis and receiving an inner end of the screw. Removal of this screw allows the knob, which is typically splined to the adjustment element, to be removed and reset with ease.
The interengaging formations include an axially open groove having a pair of ends constituting abutments and an axially projecting screw head and rotationally fixed relative to the hub and received in the groove. The groove is formed in the knob and the screw head is carried on a yoke rotationally coupled to the hub. The groove is arcuate, centered on the hub axis, and has an arc length of substantially less than 360xc2x0.
A ratchet mechanism operatively engaged between the hub and the adjustment element releasably retains same against relative angular movement in a plurality of angularly offset positions. The adjustment mechanism includes a yoke axially displaceable but rotationally fixed on the hub. The ratchet is an axially spring-biased element angularly fixed on the yoke and a plurality of axially open seats receiving the element and formed on the adjustment element.